This library provides a simplified C++ encapsulation of the system interface to TCP/IP socket stream sockets. This chapter provides:
An overview of the library, its main class (CSocket)
and the exceptions objects of this class can throw.
Instructions for including the library in your applications at both the source level and at link time.
This tutorial information is no substitute for the reference pages:
The library supports three types of sockets.
These sockets initiate connections with some service. Once connected typically they will make requests of the program that manages that service and that program will fulfil those requests as well as send response data back to the client
These sockets define a service and passively await connections.
When a connection is made, a new CSocket
object is created and the client and server subsequently
communicate over that new socket until their interaction
is complete.
An encapsulated socket is one that has been opened by
directly invoking the socket(2) operation. If you know
the socket state (more about socket states later),
you can wrap that socket in a CSocket
class.
It is important to know that sockets are a stateful entity. The
` CSocket::State and an internal state member variable
that captures this. Depending on the state of the object, some
operations may be illegal. Invoking an operation that is forbidden
by the current state will cause the object to throw a
CTCPBadSocketState exception.
A socket can be in one of the following states:
When a socket is initially created, or after it has been detected that the peer has closed its end of the socket, the socket is Disconnected.
Disconnected sockets can be Bound, turning the socket into a server socket in the Bound state or Connected which, if successful turns the socket into a Connected client socket.
A server socket is Bound when it has been configured to offer a specific service. Once Bound an application can listen on the socket for a connection.
A server socket is listening if it it can accept
connections. This is normally the case once the
Listen is invoked. Typically
Listen is followed at some point
in time by a call to Accept
which accepts the next connection received.
Connected sockets come about in one of two ways.
Either Accept called on a server
returns a socket that is connected to a new peer, or
a client socket successfully performss a
Connect call connecting
to a server.
Connected sockets can be closed written to an read from.
The Read and Write
methods can be invoked on any connected socket to transfer data to
the peer.